Bent in shell of pressure vessel (residual stresses)

[beastgod]

I have a pressure vessel with bent in its shell. So I want to evaluate this vessel acc. ASME BPVC VIII div.2 Part 5 in elastic-plastic method.
My way-
1) I build a geometry model of the vessel with the bent.
2) Use the appropriate procedure describing in ASME

Here I have a question-
When the bent was created, it have become to have residual stresses, which I haven`t taken into account. So my evaluation of vessel is wrong?
So, to evaluate this vessel right-
1)I have to model the vessel WITHOUT the bent, then to model the creation of bent (e.g. by indentor). So I get residual stresses and then
2) Use the appropriate procedure describing in ASME

Am I right?
Thanks for advance!

 

[TGS4]

The latter option may be more technically defensible. However, I have done that type of analysis both ways. If you have the time and inclination, I would suggest that you do both, compare the results, and then publish that comparison at PVP2016.

 

[MJCronin]

beastgod......

How big is the defect ???

Can you give us pictures ?

MJCronin
Sr. Process Engineer

 

[beastgod]

to TGS4-
OK, thanks for invitation, I will try to compare.

to MJCronin-
Here pictures:
sizes of bents

http://files.engineering.com/getfile.aspx?folder=d3a86f5d-3858-4727-ae06-e3d756d91c03&file=1.png.

a general form

http://files.engineering.com/getfile.aspx?folder=cbca2b13-3191-4d15-a33d-49bb3b95a726&file=2.png

angle distribution map (degrees)

http://files.engineering.com/getfile.aspx?folder=cae3e5ef-3d43-4836-a720-502110561c1b&file=3.jpg

Diameter is 2400 mm and thickness is 3 mm. Pressure is 0.3 MPa.

How can you predict whether we should model residual stresses or not? By experience?
Thank you

 

[DBreyer]

I would recommend you use API 579-1/ASME FFS-1 "Fitness-for-Service". There is a special chapter for shell distortion, bulges and dents.


Daniel Breyer
Inspection Engineer

http://lnkd.in/dFcQA-w

 

[racookpe1978]

The "picture" is more a "map" or location for the problem spots.

What do the bends and dents look like? The actual shape of the edges of the bent steel are the stress risers, and the physical shape of each indent is (I am assuming the dents go "into" the tank!) very important. Some curves may be shallow and not very important even though they are larger, another very important if the shape creates a sharper kink.